Pump

ABSTRACT

There is disclosed a pump, in particular a reciprocating pump. In one embodiment, a reciprocating pump ( 10 ) is disclosed which comprises an actuating cylinder ( 12 ); an actuating piston ( 16 ) mounted for reciprocating movement within the actuating cylinder; a discharge cylinder ( 52 ); a sleeve ( 40 ) releasably mounted within the discharge cylinder, to thereby define an operating diameter of the discharge cylinder; and a discharge piston ( 30 ) coupled to the actuating piston and mounted for reciprocating movement within the sleeve to successively draw fluid into and discharge fluid from the discharge cylinder. There is also disclosed a sleeve for such a pump, and a method of changing output flow from such a pump.

FIELD OF THE INVENTION

The present invention relates to a pump. In particular, but not exclusively, the present invention relates to a reciprocating pump.

BACKGROUND OF THE INVENTION

Pumps are commonly used in hydraulic systems for the supply of fluid under pressure. There exist a range of different types of pump. For example, single piston reciprocating pumps are known, which, in operation, draw fluid in during part of a cycle of the pump, and discharge fluid during another part of the cycle. Such pumps, however, provide an intermittent flow output, which may be undesirable.

Dual-piston reciprocating pumps are also known, which provide a substantially constant fluid output. Such pumps include opposed pistons, which are successively actuated, such that during discharge of one of the pistons, the other piston is being charged, and vice versa. Joining the two outlets of the pistons into a common fluid line facilitates constant fluid flow into the line (during the cycle of the pump), giving a constant flow output. These reciprocating dual-piston pumps are typically mechanically driven, for example using a rotating cam arrangement to drive the pistons.

However, in other arrangements, the pumps may be fluid operated, with an actuating fluid supplied to the pump to drive the pistons in a reciprocating fashion. One such type of pump is pneumatically actuated and includes a main actuating piston. The actuating piston is mounted between and coupled to the discharge pistons and is pneumatically controlled for reciprocating motion, to alternately charge and discharge the pistons.

A number of problems persist with existing single and dual-piston reciprocating pumps. For example, it is not possible to vary the flow characteristics of the pumps, or to customise the flow output for different applications. In addition, maintenance can be difficult, and can require the pumps to be substantially dismantled in order to change out components, which is undesirable.

Also, in dual-piston fluid-driven reciprocating pumps, the flow of fluid into the pump for driving the pump pistons needs to be appropriately controlled. Typically, this is achieved by incorporating flow valve assemblies into and configured for the pump. However, provision of a valve assembly in this manner inhibits maintenance of and access to the valve assembly should it require changing out. For example, in existing pump and valve assemblies, it is often difficult to replace various seals, which tend to deteriorate relatively quickly over time.

SUMMARY OF THE INVENTION

It is amongst the objects of embodiments of the present invention to provide a pump that obviates or at least mitigates some of the drawbacks and disadvantages of prior art pumps.

Further aims and objects will become apparent from the description below.

According to a first aspect of the invention, there is provided a reciprocating pump comprising:

-   -   an actuating cylinder;     -   an actuating piston mounted for reciprocating movement within         the actuating cylinder;     -   a discharge cylinder;     -   a sleeve releasably mounted within the discharge cylinder, to         thereby define an operating diameter of the discharge cylinder;         and     -   a discharge piston coupled to the actuating piston and mounted         for reciprocating movement within the sleeve to successively         draw fluid into and discharge fluid from the discharge cylinder.

In this way, the sleeve can be changed out for maintenance or replacement with different diameter sleeves, to alter the nature of the fluid discharge. For example, the pump operates by reciprocating the actuating piston within the actuating cylinder, which causes the discharge piston to correspondingly reciprocate within the sleeve. During a cycle of the pump, a fluid volume is drawn into the sleeve by the discharge piston, and is then forced out of the sleeve and the discharge cylinder at pressure. The volume of fluid drawn in and expelled in each cycle is controlled by the operating diameter of the sleeve; i.e. a relatively large diameter sleeve provides for discharge of a relatively large volume of fluid, whereas a relatively small diameter sleeve provides for discharge of a relatively small volume of fluid, but at a higher pressure. It will therefore be understood that, in combination with the discharge piston, the sleeve defines a maximum operating volume of the discharge cylinder.

Preferably, the discharge piston is removably or releasably coupled to the actuating piston. This facilitates removal and replacement of the piston, such that a range of discharge pistons may be provided, each of which corresponds to a different diameter sleeve. This may also facilitate maintenance.

Preferably also, the discharge cylinder is removably or releasably coupled to the actuating cylinder. In this way, the discharge cylinder can be detached and the discharge piston replaced with a new piston, together with appropriate seals and a desired sleeve, which correspond to the chosen size of the new piston.

Preferably, the pump additionally comprises:

-   -   a second discharge cylinder;     -   a second sleeve releasably mounted within the second discharge         cylinder, the second sleeve defining an operating diameter of         the second discharge cylinder; and     -   a second discharge piston coupled to the actuating piston and         mounted for reciprocating movement within the second sleeve, to         successively draw fluid into the second discharge cylinder while         discharging fluid from the first discharge cylinder, and to         discharge fluid from the second discharge cylinder while drawing         fluid into the first discharge cylinder.

In this way, the pump can achieve a substantially constant fluid output. The first and second sleeves may be independently replaceable and may have different operating diameters. In this fashion, the output of discharged fluid may be balanced to achieve relatively high-pressure and high-flow volume; this may be achieved by combining a relatively high volume, low pressure flow from one discharge cylinder (using a relatively large diameter sleeve) with a relatively low volume, high pressure flow from the other piston (using a relatively small diameter sleeve). Accordingly, this may facilitate control of the physical characteristics, such as pressure and flow rate, of the fluid discharged from the pump.

Alternatively, the pump may provide separate, independent fluid outputs from the two cylinders, which may therefore have different flow characteristics.

In a further alternative, the second discharge sleeve has an operating diameter equal to the operating diameter of the first discharge sleeve.

Preferably, the second discharge piston is removably coupled to the actuating piston. The second discharge cylinder may also be removably attached to the actuating cylinder.

Optionally, the first and second discharge cylinders are located at opposing first and second ends of the pump.

This facilitates effective transfer of force from the actuating piston to the discharge pistons.

The pump may further include a seal for sealing between the sleeve and the discharge cylinder. Where the pump includes two discharge pistons, the pump may comprise first and second seals for sealing between the first and second discharge pistons and the respective sleeves. This may prevent leakage of fluid between the pistons and the sleeves.

Preferably, the diameters of the first and second discharge pistons are matched to the respective diameters of the first and second sleeves, for slideable movement of the discharge pistons within the sleeves.

The sleeve may be tubular, and may form part of a removable cartridge, which may comprise the sleeve and the seal. The cartridge or the pump may further comprise a locking collar, which may comprise threads for engaging with mating threads provided in the discharge cylinder. The locking collar may serve for locating and securing the sleeve against movement relative to the discharge cylinder, in use.

It will be understood that the actuating piston operates in response to a fluid pressure force provided by an actuating fluid. Preferably, the actuating fluid is a gas, and may be a pneumatic fluid, particularly, compressed air. Alternatively, the actuating fluid is a liquid.

Preferably, the pump comprises a main valve assembly for controlling supply of actuating fluid to the actuating piston. The main valve assembly may be adapted for controlling supply of actuating fluid successively to one end of the actuating cylinder acting on one face of the actuating piston, whilst permitting discharge of actuating fluid from the other end of the actuating cylinder acting on an opposite face of the actuating piston. In this way, the actuating fluid acts successively on opposing faces of the actuating piston, to cause the reciprocating movement.

The main valve assembly may comprise a valve housing and a reciprocating shuttle valve, which may control the flow of actuating fluid to the actuating cylinder depending upon a position of the shuttle valve in the housing. Preferably, the main valve assembly, and in particular the valve housing and the shuttle valve, is provided separately from the actuating cylinder. This allows the shuttle valve to be maintained and changed out without a need to dismantle other pump components.

The actuating cylinder may comprise a plurality of fluid flow ports for fluid communication between the actuating cylinder and the main control valve assembly. In a preferred embodiment, the actuating cylinder comprises a pair of main flow ports, for the flow of actuating fluid in to and out of the cylinder. The main flow ports may act as inlets or outlets depending on a direction of movement of the actuating piston.

The main actuating cylinder flow ports may be in fluid communication with the main valve assembly through main valve assembly flow ports, for the flow of fluid between the actuating cylinder and the main valve assembly. In a first position, the shuttle valve may facilitate supply of actuating fluid to a first end of the actuating cylinder and discharge from a second end, to facilitate movement of the actuating piston in a first direction. In a second position, the shuttle valve may facilitate supply of actuating fluid to the second end and discharge from the first end, for movement of the actuating piston in a second, opposite direction. This may provide the desired reciprocating motion of the actuating piston.

Preferably, the actuating cylinder includes a pair of pilot valves for controlling operation of the main valve assembly. The pilot valves may be provided at opposite ends of the actuating cylinder, and may each include a valve pin protruding into the actuating cylinder for opening the pilot valves. The pilot valves may be biased toward a closed position, and the actuating piston may be adapted to open the pilot valves via mechanical interaction between the actuating piston and the pilot valves, optionally with the pin of each valve.

The pilot valves may permit selective fluid bleed from the main valve housing. In particular, each pilot valve may selectively permit fluid bleed from a respective end of the main valve housing. In this fashion, opening of one of the pilot valves may facilitate movement of the shuttle valve between its first and second positions, to thereby switch supply of actuating fluid between the main valve assembly and the actuating cylinder. The pilot valves may selectively open the main valve housing to atmosphere, to permit fluid bleed, through respective bleed ports.

In an alternative, a first pilot valve may be coupled to a first end of the main valve housing, and a second pilot valve to a second, opposite end of the valve housing, by corresponding fluid lines. The pilot valves may each also be coupled to a fluid pressure source. Actuation of the first pilot valve may supply fluid to the first end of the valve housing, to move the shuttle valve in a first direction. Actuation of the second pilot valve may supply fluid to the second end of the valve housing, to move the shuttle in a second, opposite direction.

The position of the pins relative to the actuating cylinder may be adjustable, or the pins may be adjustable in length. Thus, advantageously, the distance of travel of the actuating piston can be altered to correspondingly change the duration of successive discharge and draw-in phases from first and second ends of the pump.

Preferably, the main valve assembly further comprises a flow input valve coupled to the valve housing, for controlling supply of actuating fluid to the assembly. The flow input valve may be needle valve, and may be adjustable for controlling the supply of fluid to the main valve assembly and thus to the actuating piston. This may facilitate variation of an operating characteristic of the pump, such as output fluid pressure or flow rate.

According to a second aspect of the present invention, there is provided a sleeve for a reciprocating pump, wherein the sleeve is adapted to be releasably mounted in a discharge cylinder of the pump, to thereby define an operating diameter of the discharge cylinder.

Preferably, the sleeve is further adapted to receive a discharge piston of the pump, the discharge piston coupled to an actuating piston of the pump and mounted for reciprocating movement within the sleeve to successively draw fluid into and discharge fluid from the cylinder.

Preferably, the sleeve is for a reciprocating pump according to the first aspect of the invention.

Other characteristics of the sleeve are defined in relation to the first aspect of the invention.

According to a third aspect of the invention, there is provided a method of changing output flow from a pump comprising the steps of:

-   -   detaching a discharge cylinder from a pump;     -   releasing a first sleeve of a first diameter from location         within the discharge cylinder;     -   inserting a second sleeve of a second, different, diameter into         the discharge cylinder; and then     -   re-attaching the discharge cylinder to the pump.

Preferably, the method comprises the steps of:

-   -   releasing a first discharge piston from the pump, the first         discharge piston adapted for reciprocating movement within the         first sleeve;     -   attaching a second piston sized to be received within the second         sleeve; and then     -   re-attaching the discharge cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

There will now be described, by way of example only, embodiments of the present invention, with reference to the following drawings, in which:

FIG. 1 is a longitudinal, cross-sectional view of a reciprocating pump in accordance with an embodiment of the present invention;

FIG. 2 is a view of the pump shown in FIG. 1, also illustrating a main valve assembly of the pump, the pump shown at a stage in a cycle of operation of the pump;

FIG. 3 is a view of the pump of FIG. 2 shown at a further stage in the cycle of operation of the pump;

FIG. 4 (presented on same sheet as FIG. 1) is an enlarged, exploded view of a discharge cylinder and a sleeve which form part of the pump shown in FIG. 1;

FIG. 5 is a longitudinal, cross-sectional view of a reciprocating pump in accordance with an alternative embodiment of the present invention;

FIG. 6 is a longitudinal, cross-sectional view of a main valve assembly forming part of a reciprocating pump in accordance with a further alternative embodiment of the present invention;

FIGS. 7 and 8 are longitudinal, cross-sectional views of a main valve assembly forming part of a reciprocating pump in accordance with a preferred embodiment of the present invention, with a shuttle of the valve assembly shown at opposite extents of movement; and

FIGS. 9 and 10 are views similar to those of FIGS. 7 and 8 of a main valve assembly of a reciprocating pump in accordance with a further alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Turning firstly to FIG. 1, there is shown a longitudinal, cross-sectional view of a pump in accordance with an embodiment of the present invention, the pump indicated generally by reference numeral 10. The pump 10 is illustrated in more detail in FIGS. 2 and 3, which also show a main valve assembly 80 of the pump 10, and which show the pump 10 at various stages in a cycle of operation.

The pump 10 comprises an actuating cylinder 12 and an actuating piston in the form of an air drive flange 16, which is mounted for reciprocating movement within the actuating cylinder 12. The pump also comprises a discharge cylinder 52 a which is provided in a hydraulic end housing 38 a, and a sleeve in the form of a cartridge 40 a which is releasably mounted within the discharge cylinder 52 a, to thereby define an operating diameter 42 a of the cylinder. Additionally, a discharge piston 30 a is coupled to the flange 16 and mounted for reciprocating movement within the sleeve 40 a, to discharge fluid from the discharge cylinder 52 a.

In use, the pump 10 is operated to pump a fluid by controlling reciprocating movement of the flange 16 within the actuating cylinder 12. This is achieved by controlling the supply of actuating fluid (in this case, compressed air) to the actuating cylinder 12, as will be described in more detail below. The discharge piston 30 a, by virtue of its connection to the flange 16, is reciprocated back and forth within the sleeve 40 a during movement of the flange 16, and thus repeatedly charges the discharge cylinder 52 a (drawing fluid in through a check valve in an inlet 56 a) and discharges the cylinder 52 a (expelling the fluid through a check valve in an outlet 58 a).

As noted above, the sleeve 40 a is releasably mounted within the discharge cylinder 52 a, which facilitates maintenance and/or replacement. Indeed, the sleeve 40 a may be replaced with a sleeve of a different internal diameter, which enables the flow characteristics of the pump to be adjusted. For example, by replacing the sleeve 40 a with a sleeve of a smaller internal diameter, a smaller volume of fluid is drawn into the discharge cylinder 52 a on each cycle of the discharge piston 30 a. However, as the diameter of the replacement sleeve 40 a is smaller, the resultant pressure of the discharged fluid is higher; this is due to the corresponding smaller piston area defined by the replacement sleeve, which will be described below.

The structure and method of operation of the pump 10 will now be described in more detail. The pump 10 is a dual-piston reciprocating pump, for supplying a substantially constant fluid output, and includes two discharge pistons 52 a, 52 b at opposite ends 32 and 34 of the pump. Like components of the pump components at the end 32 with those at the end 34 share the same reference numerals, but with the suffix ‘a’ generally replaced with the suffix ‘b’.

The air cylinder 12 includes end caps 14 a,b and a drive shaft 18 is provided which extends along a longitudinal axis of the cylinder 10 and through apertures 20 a,b in the end caps 14 a,b. The air drive flange 16 is connected to the portion 22 of the shaft 18 within the cylinder 12, and seals 24 are provided around the outer circumference of the flange 16. The discharge pistons 30 a,b are connected to the drive shaft 18 via threaded connections 36 a,b thereby allowing the pistons to be readily changed out.

Hydraulic end housings 38 a,b are connected to each end 32, 34 of the pump, and are threadably connected to the end caps so that they can be removed easily for access to components of the pump. The hydraulic end housings 38 a,b define the discharge cylinders 52 a,b and are aligned with the longitudinal axis of the pump, such that the drive shaft 18 with pistons 30 a,b are able to slideably move relative to the discharge cylinders. The housings 38 a,b include respective end portions or caps 50 a,b.

The hydraulic end housings 38 a,b receive the sleeves or cartridges 40 a,b, which have hydraulic seals 44 a,b that seal between the cartridges 40 a,b and the outer surface of the pistons 30 a,b. The diameter 42 a,b defined by the cartridges 40 a,b match that of the pistons 30 a,b such that the pistons fit snugly and slideably within the cartridges.

The seals 44 a,b and cartridge 40 a,b are secured in position in the hydraulic end housings 38 a,b by packing nuts 46 a,b which are threadably connected to the housing. In this way, the cartridges are removable from the end housings and the pump. The hydraulic end housing 38 a and cartridge 40 a are shown detached from the pump in the enlarged, exploded view of FIG. 4, which is presented on the same sheet as FIG. 1.

In use, a maximum, operating volume of the discharge cylinders 52 a,b are defined by front surfaces 54 a,b of the pistons 30 a,b, the inner surfaces of the cartridges 40 a,b, and end portions 50 a,b of the hydraulic end housings and depend upon the extent of movement of the pistons relative to the cartridges.

The inlets 56 a,b enable fluid to be drawn in from an external reservoir (not shown), whilst the discharge pistons 30 a,b move in a direction away from the respective first and second ends 32, 34 of the pump. The outlets 58 a,b facilitate discharge of high-pressure fluid from the cylinders 52 a,b under the force of the pistons 30 a,b.

By this arrangement, the pump 10 is modular and the detachable hydraulic end housings 38 a,b allow easy access to the pistons 30 a,b and hydraulic seals 44 a,b. This facilitates cleaning/maintenance and replacement without having to fully dismantle the pump 10.

The provision of removable pistons and cartridges also allows pistons of different sizes to be selected and installed with ease, in situ, and without requirement to change other pump components. To achieve this, different cartridges 40 a,b provided with different size internal bores are inserted into the end housings 38 a,b with internal diameters corresponding to the outer diameters of the desired pistons 30 a,b.

Thus, a piston may be changed out and replaced with a different piston as required by a user for a particular application. For example, a smaller piston may be required to provide high-pressure, low-flow-rate output. The provision of different cartridge or insert sizes removes the need to provide pumps with different specifications for different jobs or purposes.

The air cylinder is additionally provided with ports 57 a,b extending through the cylinder end caps 14 a,b. As will be described, the ports 57 a,b provide a fluid connection to ends 26 and 28 of the air cylinder 12 for driving the pump 10.

In FIG. 2, the pump 10 is shown in an operational configuration, connected to a main valve assembly 80. In use, air is supplied to the air cylinder 12 under the control of the valve assembly 80, which comprises a valve housing 98 and a shuttle valve 100. The shuttle valve 100 is mounted for reciprocating movement within the housing 98, and is provided with a number of flanges 102 having outer surfaces 104 which carry seals 106. The flanges 102 of the shuttle valve 100 defines a series of annular chambers 82, 84, 90 and 92 between the shuttle valve and the valve housing 98, which serve for controlling air flow, as will be described below.

The valve assembly 80 also includes an adjustable needle valve 83, through which air enters the valve assembly for driving the pump 10. Air enters the valve assembly 80 via a port 81, and flows into the chamber 82. In the portion of the pump cycle depicted in FIG. 2, the air provided to chamber 82 exits through a port 85 and flows into the air cylinder 12 via a pipe 94 a and the port 57 a. This air enters the end 26 of the cylinder 12 under pressure, and exerts a pressure force on the drive flange 16. Simultaneously, the end 28 of the air cylinder 12 is open to atmosphere, via the port 57 b, a pipe 94 b, a port 87 in the valve housing 98 and an exhaust port 89 (which opens on to the annular chamber 84). A pressure differential is thereby created across the flange 16, which then moves towards the second end 34 of the pump. The piston 30 b connected to the drive shaft 18 acts against the fluid in the chamber 52 b, providing a high-pressure output from outlet 58 b. The pressure of the air provided to the air cylinder 12 is typically between 2 and 12 bar (approximately 30 to 175 psi), whilst the output pressure is in the region of 60,000 psi.

The pump 10 also comprises two pilot valves 60 a,b which are biased closed, and which are opened via mechanical activation of valve pins 66 a,b from inside the air cylinder 12. The length of the pins 66 a,b is adjustable and the pins 66 a,b protrude into the cylinder ends 26 and 28.

At the end of the above phase of the drive cycle, the flange 16 strikes the valve pin 66 b of the pilot valve 60 b and, when the pin is depressed, the valve is opened. As shown in FIG. 2, the pilot valves 60 a,b are connected via pipes 96 a,b to ports 88 a,b of the flow valve. Air is supplied to the pipes from a common pressure source (not shown) through ports 86 a,b of the valve assembly 80 and annular end chambers 90 and 92 respectively. Air pressure in these pipes 96 a,b and the chambers 90 and 92 determine the position of the shuttle valve 100 within the valve housing 98. In the position of FIG. 2, the pressure in the chamber 90 is held at a higher level than that in the chamber 92 by the closed pilot valve 60 b, creating a pressure differential across the shuttle valve 100 holding it in the FIG. 2 position.

When the valve 60 b is opened, through contact between the flange 16 and the valve pin 66 b, the air in the pipe 96 b is vented to atmosphere through a pilot hole (not shown) which is opened by this movement of the valve pin 66 b. The pressure in pipe 96 b and chamber 90 thus reduces to near atmospheric pressure, urging the shuttle 100 towards the now-low pressure chamber 90, driven by the higher pressure of air in chamber 92, moving the shuttle 100 to the position shown in FIG. 3.

Thus referring now to FIG. 3, the pump is shown following movement of the shuttle 100 to the opposite end of the valve housing 98. In this position, the chamber 82 of the valve assembly 80 opens onto the port 87, such that air is now provided to the end 28 of the air cylinder 12 through port 57 b. In a similar manner to the cycle described above with reference to FIG. 2, air is supplied to the cylinder end 28 and forces the flange 16 and piston 30 to move toward the first end 32 of the pump 10. In this case, air exits the cylinder end 26 via port 57 a and pipe 94 a and back to the valve assembly 80. The return air enters port 85 and exhausts to the atmosphere through a port 126. After the flange 16 commences movement towards the pump end 32, the pilot valve 62 b is released and closes, locking the shuttle 100 in the position of FIG. 3.

This part of the cycle ends when the flange 16 comes into contact with the pilot valve pin 66 a, exhausting air from chamber 92 to atmosphere (through the line 94 a and valve 62 a), such that the pressure of the air in chamber 90 returns the shuttle 100 to the left, to the position of FIG. 2. A continuous reciprocating two-way pump cycle is thus produced by providing a constant air flow to the valve assembly 80, and a common pressure source to ports 86 a,b.

In use of the pump 10, the different internal diameters 42 a,b of the sleeves 40 a,b result in different flow characteristics of the discharged fluid. In particular, a larger volume of fluid is discharged from the cylinder 52 a on each cycle of the piston 30 a than on each cycle of the piston 30 b. However, the smaller piston area of the piston 30 b results in a higher pressure output from the discharge cylinder 52 b. By combining the outputs from the cylinders 52 a and 52 b, a balance of a good flow rate and pressure can be achieved.

The present invention provides a number of other advantages. The pins 66 a,b for triggering the switching of the stroke direction of the pump are adjustable in length. This allows the stroke length of the pump in either direction to be adjusted, i.e. arranging the pins to protrude further into the air cylinder 12 will shorten the stroke length. The valves containing these pins may be unscrewed to insert appropriate length pins 66 a,b or the lengths of the pins could be adjusted externally without needing to unscrew the valve. In either case, the pins and stroke length can be adjusted easily without dismantling the pump or providing a different size cylinder, which would otherwise be necessary.

Turning now to FIG. 5, there is shown a longitudinal, cross-sectional view of a reciprocating pump in accordance with an alternative embodiment of the present invention, the pump indicated generally by reference numeral 10′. Like components of the pump 10′ with the pump 10 of FIGS. 1 to 4 share the same reference numerals, with the addition of the suffix′. Only significant differences between the pump 10′ and the pump 10 will be described in detail herein. The pump 10′ includes pilot valves 60′a and 60′b which govern the position of a shuttle valve 100′, in a similar fashion to the valves 60 a, 60 b of the pump 10. However, end caps 14′a and 14′b of an actuating cylinder 12′ include bleed vents 108 a, 108 b which open on to bores 110 a, 110 b in which the respective valves 60′a, 60′b are mounted. The bleed vent 108 a is coupled to a fluid outlet line 112 a which is in fluid communication with a chamber 90′ of the valve assembly 80′. In a similar fashion, the bleed vent 108 b is coupled by a fluid outlet line 112 b to a chamber 92′ at an opposite end of the valve 80′. The valves 60′a and 60′b are coupled via fluid supply lines 96′a and 96′b to a common pilot pressure source (not shown). Ports 86′a and 86′b of the shuttle valve 80′ carry one-way valves (not shown), and permit exhaust of air from the chambers 92′ and 90′, respectively.

The pump 10 operates as follows. In use and during movement of a flange 16′ of the pump 10′ to the right, as shown in FIG. 5, the flange 16′ comes into contact with a pin 66′b of the pilot valve 60′b. This causes the valve 60′b to open, thereby permitting fluid communication between the pilot pressure source and the chamber 92′, through the supply line 96′b and the outlet line 112 b. The valve 60′a is closed, and the fluid supplied to chamber 92′ causes the shuttle valve 100′ to move to the right, exhausting the air in chamber 90′ through the port 86′b. In a similar fashion to the valve assembly 80 of the pump 10, this switches flow into the actuating cylinder 12′, and reverses the flange 16′.

When the flange 16′ strikes a pin 66′a of the pilot valve 60′a, fluid communication between the pilot pressure source and the chamber 90 through the inlet line 96′a and outlet line 112 a is opened. This permits fluid communication between the pilot pressure source and the chamber 90′, through the supply line 96′a and the outlet line 112 a. The shuttle valve 100′ is thus urged back to the left, exhausting the air in chamber 92′ through the port 86′a. This reverses flow into the actuating cylinder 12′ once again.

It should be noted in FIG. 5 that the pump 10′ includes sleeves 40′a and 40′b which are of similar internal diameters, and thus illustrates a situation where it is desired to have similar discharge from each discharge piston 30′a and 30′b. Additionally, FIG. 5 illustrates clamping bolts 116 which secure the cylinder flanges 14′a, 14′b together.

Turning now to FIG. 6, there is shown a longitudinal, cross-sectional view of a main valve assembly forming part of a reciprocating pump in accordance with a further alternative embodiment of the present invention, the main valve assembly indicated generally by reference numeral 80″. The valve assembly 80″ typically forms part of a pump similar to the pump 10′ shown in FIG. 5, and thus may replace the valve assembly 80′. For ease of illustration, only the valve assembly 80″ is shown in FIG. 6 and described, the remaining components of the pump being as shown in FIG. 5. Only the differences between the assemblies 80″ and 80′ will be described herein in detail, and like components of the valve assembly 80″ with the valve assemblies of FIGS. 1 to 4 and FIG. 5 share the same reference numerals, with the addition of the suffix ″.

The valve assembly 80″ includes a shuttle 100″ of slightly different shape to the shuttle 100′ of the valve assembly 80′. Specifically, the shuttle 100″ includes shoulders 118, 120 which abut end caps 122, 124 respectively at each extreme extent of travel of the shuttle 100″. These end caps 122, 124 are threadably coupled to a housing 98″ of the valve assembly 80″, in a similar fashion to the valve assemblies shown in FIGS. 1 to 5. This permits removal of the shuttle 100″ for maintenance/replacement. The shoulders 118, 120 define maximum extents of movement of the shuttle 100″, and thus the position of the shuttle 100″ in relation to the various ports 85″; 86″a,b; 87″; and 88″a,b. Additionally, the end cap 124 defines an outlet 126 from an end chamber 128 which is of larger diameter than similar vent or bleed ports from the valve assemblies shown in FIGS. 1 to 5. This provides improved exhaust of air from the chamber 128 in use of the valve assembly 80″. Operation of the valve assembly 80″ is otherwise as described in relation to the valve assembly 80′ of FIG. 5.

Turning now to FIGS. 7 and 8, there are shown longitudinal, cross-sectional views of a main valve assembly forming part of a reciprocating pump in accordance with a preferred embodiment of the present invention, the valve assembly indicated generally by reference numeral 80′″ and shown in the Figures at respective opposite extents of travel of a shuttle 100′″ of the valve assembly.

As with the valve assembly 80″ of FIG. 6, the valve assembly 80′″ is provided as part of a reciprocating pump similar to that shown in FIG. 5, save that the valve assembly 80′ has been replaced with the valve assembly 80′″. The remaining components of the pump have been omitted, for ease of illustration. Furthermore, only the differences between the valve assembly 80′″ and the previously described valve assemblies will be described herein in detail. Like components of the valve assembly 80′″ with the valve assemblies of FIGS. 1 to 4, FIG. 5 or FIG. 6 share the same reference numerals, with the addition of the suffix ′″.

A housing 98′″ of the valve assembly 80′″ includes a number of flow ports 130 a and 130 b (two of each shown) spaced around a circumference of the housing 98′″. Outer seal rings 132 a, 132 b are mounted on the housing 98 in abutment with a central flange 134, and are secured by bolts (not shown) which extend through passages 136 a,b and engage in the flange 134. The seal rings 132 a,b define main flow ports (not shown) similar to the ports 85″ and 87″ of the valve assembly 80″. These main flow ports open onto annular chambers 138 a,b between the seal rings 132 a,b and the housing 98′″, as do the flow ports 130 a, 130 b. This provides fluid communication between the valve assembly 80′″ and the cylinder of the pump (such as the cylinder 12′ of the pump 10′ shown in FIG. 5). This arrangement of the flow ports 130 a,b spaced around the circumference of the housing 98′″, and of the main flow ports opening onto the annular chambers 138 a,b provides enhanced flow of air to and from the cylinder in use of the valve assembly 80′″.

Additionally, end caps 122′″ and 124′″ of the valve assembly 80′″ have enlarged outlets 126′″a, 126′″b, to provide enhanced flow of exhaust air. The shuttle 100′″ also includes a number of exhaust ports 140 and 142 (five of each shown) spaced around a circumference of the shuttle valve, to enhance flow of exhaust air. Finally, the shuttle 100′″ includes a throughbore 144 which provides for fluid communication between the exhaust ports 140, 142 and the respective outlets 126′″a,b. The shuttle 100′″ is shown following movement to the opposite extent of its travel in FIG. 8.

Turning now to FIGS. 9 and 10, there are shown views similar to those of FIGS. 7 and 8 of a main valve assembly 80 ^(iv) of a reciprocating pump in accordance with a further alternative embodiment of the present invention, the valve assembly indicated generally by reference numeral 80 ^(iv) and illustrated at opposite extents of movement in FIGS. 9 and 10. As with the valve assembly 80″ of FIG. 6, the valve assembly 80 ^(iv) is provided as part of a reciprocating pump similar to that shown in FIG. 5, save that the valve assembly 80′ has been replaced with the valve assembly 80 ^(iv). The remaining components of the pump have been omitted, for ease of illustration. Furthermore, only the differences between the valve assembly 80 ^(iv) and the previously described valve assemblies will be described herein in detail. Like components of the valve assembly 80 ^(iv) with the assemblies of FIGS. 1 to 4, FIG. 5, FIG. 6 or FIGS. 7 and 8 share the same reference numerals, with the addition of the suffix ^(iv).

The valve assembly 80 ^(iv) is essentially the same as the valve assembly 80′″, save that the internal diameter of the shuttle 100′″ throughbore 144 is ¾″, whereas a throughbore 144 ^(iv) of the shuttle 100 ^(iv) is 1″ to provide enhanced air flow. Additionally, internal diameters of end caps 122 ^(iv) and 124 ^(iv) have been enlarged to account for the larger diameter shuttle 100 ^(iv). Operation of the valve assemblies 80′″ and 80 ^(iv) is otherwise as described in relation to the valve assembly 80′ of FIG. 5.

Other characteristics of the pumps described above may also be customised for different applications by the provision of detachable end housings. The end housings may be detached, allowing the piston to be unscrewed and replaced with a different diameter piston to suit desired needs. Cartridges provided in the housing that compliment the piston and house the hydraulic seals can similarly be unscrewed, removed and replaced. Such replacement can be carried out with ease and with the pump in situ, as part of a larger system. Hydraulic seals can be easily accessed, maintained and replaced.

The present pump mitigates the need to dismantle the pump or to change out the entire pump with a new pump when different pump characteristics are required. This saves costs relating to the purchase of parts and operational downtime for repair and maintenance.

Various modifications and improvements may be made to the foregoing without departing from the spirit and scope of the present invention.

For example, the discharge pistons may be directly threadably coupled to the actuating piston, such that the entire piston is released from the actuating piston when it is desired to changeover for a discharge piston of a different diameter. 

1. A reciprocating pump comprising: an actuating cylinder; an actuating piston mounted for reciprocating movement within the actuating cylinder; a discharge cylinder; a sleeve releasably mounted within the discharge cylinder, to thereby define an operating diameter of the discharge cylinder; and a discharge piston coupled to the actuating piston and mounted for reciprocating movement within the sleeve to successively draw fluid into and discharge fluid from the discharge cylinder.
 2. A pump as claimed in claim 1, wherein the discharge piston is releasably coupled to the actuating piston.
 3. A pump as claimed in claim 1, wherein the discharge cylinder is releasably coupled to the actuating cylinder.
 4. A pump as claimed in claim 1, wherein the pump additionally comprises: a second discharge cylinder; a second sleeve releasably mounted within the second discharge cylinder, the second sleeve defining an operating diameter of the second discharge cylinder; and a second discharge piston coupled to the actuating piston and mounted for reciprocating movement within the second sleeve, to successively draw fluid into the second discharge cylinder while discharging fluid from the first discharge cylinder, and to discharge fluid from the second discharge cylinder while drawing fluid into the first discharge cylinder.
 5. A pump as claim in claim 4, wherein the output from the two discharge cylinders is combined.
 6. A pump as claimed in claim 4, wherein the pump provides independent fluid outputs from the two discharge cylinders.
 7. A pump as claimed in claim 4, wherein the first and second sleeves are of different diameters, to define different operating diameters of the respective discharge cylinders.
 8. A pump as claimed in claim 4, wherein the second discharge sleeve has a diameter equal to that of the first discharge sleeve, such that the discharge cylinders are of the same operating diameters.
 9. A pump as claimed in claim 4, wherein the second discharge piston is releasably coupled to the actuating piston.
 10. A pump as claimed in claim 4, wherein the second discharge cylinder is releasably coupled to the actuating cylinder.
 11. A pump as claimed in claim 4, wherein the first and second discharge cylinders are located at opposing first and second ends of the pump.
 12. A pump as claimed in claim 1, wherein the sleeve forms part of a removable cartridge comprising the sleeve and a seal for sealing between the sleeve and the discharge cylinder.
 13. A pump as claimed in claim 1, comprising a locking collar for engaging with the discharge cylinder to locate and secure the sleeve against movement relative to the discharge cylinder, in use.
 14. A pump as claimed in claim 1, wherein the actuating piston is operable in response to a fluid pressure force provided by an actuating fluid.
 15. A pump as claimed in claim 14, comprising a main valve assembly for controlling supply of actuating fluid to the actuating piston.
 16. A pump as claimed in claim 15, wherein the main valve assembly is adapted for controlling supply of actuating fluid successively to one end of the actuating cylinder whilst permitting discharge of actuating fluid from the other end of the actuating cylinder.
 17. A pump as claimed in claim 15, wherein the main valve assembly comprises a valve housing and a reciprocating shuttle valve, the shuttle valve controlling the flow of actuating fluid to the actuating cylinder depending upon a position of the shuttle valve relative to the valve housing.
 18. A pump as claimed in claim 15, wherein the main valve assembly is provided separately from the actuating cylinder.
 19. A pump as claimed in claim 15, wherein the actuating cylinder comprises a plurality of fluid flow ports for fluid communication between the actuating cylinder and the main valve assembly.
 20. A pump as claimed in claim 19, wherein the actuating cylinder comprises a pair of main flow ports, for the flow of actuating fluid into and out of the cylinder, the main flow ports acting as inlets or outlets depending on a direction of movement of the actuating piston.
 21. A pump as claimed in claim 19, wherein the main actuating cylinder flow ports are in fluid communication with the main valve assembly through main valve assembly flow ports, for the flow of fluid between the actuating cylinder and the main valve assembly.
 22. A pump as claimed in claim 17, wherein in a first position, the shuttle valve facilitates supply of actuating fluid to a first end of the actuating cylinder and discharge from a second end, to facilitate movement of the actuating piston in a first direction.
 23. A pump as claimed in claim 22, wherein in a second position, the shuttle valve facilitates supply of actuating fluid to the second end and discharge from the first end, for movement of the actuating piston in a second, opposite direction.
 24. A pump as claimed in claim 15, wherein the actuating cylinder includes a pair of pilot valves for controlling operation of the main valve assembly.
 25. A pump as claimed in claim 24, wherein the pilot valves are provided at opposite ends of the actuating cylinder, and each include a valve pin protruding into the actuating cylinder enabling opening of the pilot valves.
 26. A pump as claimed in claim 24, wherein the pilot valves are each biased towards a closed position, and wherein the actuating piston is adapted to contact the pilot valves to open the valves.
 27. A pump as claimed in claim 24, wherein the pilot valves permit selective fluid bleed from the main valve housing.
 28. A pump as claimed in claim 27, wherein each pilot valve selectively permits fluid bleed from a respective end of the main valve housing.
 29. A pump as claimed in claim 28, wherein the pilot valves selectively open the main valve housing to atmosphere, to permit fluid bleed through respective bleed ports.
 30. A pump as claimed in claim 24, wherein a first pilot valve is coupled to a first end of the main valve housing, and a second pilot valve is coupled to a second, opposite end of the valve housing, by corresponding fluid lines.
 31. A pump as claimed in claim 30, wherein the pilot valves are each also coupled to a fluid pressure source such that actuation of the first pilot valve supplies fluid to the first end of the valve housing, to move the shuttle valve in a first direction and actuation of the second pilot valve supplies fluid to the second end of the valve housing, to move the shuttle in a second, opposite direction.
 32. A pump as claimed in claim 25, wherein the position of the pins relative to the actuating cylinder are adjustable to permit alteration of the distance of travel of the actuating piston.
 33. A pump as claimed in claim 15, wherein the main valve assembly further comprises a flow input valve for controlling supply of actuating fluid to the assembly, and wherein the flow input valve is adjustable for controlling the supply of fluid to the main valve assembly and thus to the actuating piston.
 34. A sleeve for a reciprocating pump, wherein the sleeve is adapted to be releasably mounted in a discharge cylinder of the pump, to thereby define an operating diameter of the discharge cylinder.
 35. A method of changing output flow from a pump comprising the steps of: detaching a discharge cylinder from a pump; releasing a first sleeve of a first diameter from location within the discharge cylinder; inserting a second sleeve of a second, different, diameter into the discharge cylinder; and then re-attaching the discharge cylinder to the pump.
 36. A method as claimed in claim 35, further comprising the steps of: releasing a first discharge piston from the pump, the first discharge piston adapted for reciprocating movement within the first sleeve; attaching a second piston sized to be received within the second sleeve; and then re-attaching the discharge cylinder. 